Age-associated decline in KIR2DL3 core promoter methylation. CD4 T-cell, CD8 T-cell, and NK-cell DNA from 20- to 30-year-old persons (n = 13; □) and 70- to 85-year-old persons (n = 13; ▩) were treated with sodium bisulfite; methylation at CpG sites −170/−160 (A), −120/−116 (B), and −50 (C) were quantified by methylation-specific real-time PCR as described in Figure 2.